Nanosecond pulsed plasma discharge for remediation of simulated wastewater containing thiazine and azo dyes as model pollutants.

This article focuses on the use of pulsed underwater plasma discharge in an oxygen-water mixture for the degradation of thiazine (methylene blue, MB) and azo (methyl orange, MO) dyes in simulated wastewater. The study demonstrates that increasing the applied pulsed DC voltage (5–9 kV) enhances energy coupling, leading to higher gas and electron temperatures and increased concentrations of reactive species such as hydroxyl radicals and hydrogen peroxide, while ozone concentration decreases. Under optimized conditions, degradation efficiencies of 75.5% for MB and 81.4% for MO were achieved with energy yields of 3.55 and 4.73 g/kWh, respectively; activation energies for degradation were estimated as 67.17 kJ/mol for MB and 75.32 kJ/mol for MO. Analytical techniques including UV/VIS and Fourier-transform infrared spectroscopy, along with gas chromatography-mass spectrometry, confirmed dye degradation and suggested possible degradation pathways involving fragmentation into smaller organic compounds. The results indicate that this plasma-based method offers an effective, instant treatment for flowing wastewater samples without the use of hazardous chemicals, presenting a promising approach for water remediation.